Dependence on the natural exchange of air between the indoors and outdoors through air infiltration and exfiltration may not be satisfactory for good indoor air quality and moisture control. Accordingly, mechanical ventilation systems have been developed that use fans to maintain a flow of fresh outdoor air into a building (outside air stream) while exhausting out an equal amount of stale indoor air (exhaust air stream).
Unfortunately, these ventilation systems place additional burdens on the heating, ventilating, and air conditioning systems of a building. In particular, costly conditioned air is exhausted (along with contaminants) as the exhaust air stream, while the outside air stream must be brought in and conditioned (cooled, heated, and/or dehumidified) in order to provide a healthy environment in the building. Furthermore, these ventilation systems result in the loss of heating or cooling energy in the exhaust air. The problem of losing heating or cooling energy through the air exhausted from a building or facility has had a major impact in the form of wasted energy and high costs for heating, ventilating, and cooling buildings, institutions, and facilities.
This problem is exacerbated in commercial facilities and institutions that require nearly one hundred percent outside air at high ventilation rates. A pet store, veterinarian's office, or gymnasium represents a few of such facilities, but similar requirements are presented in other applications as well. The heating and cooling energy needed to condition this air, as well as the fan energy needed to move it, can be prohibitively costly. Moreover, with the high percentage of outdoor air mandated for commercial and institutional buildings, controlling indoor humidity levels can become a challenge.
Strategies for recovering at least a portion of this wasted energy have concentrated on separate systems and methods for recovering the lost heating or cooling energy through cross flow exchangers, run-around loops, heat wheels, heat pipes, and so forth. Each of these strategies try to scavenge the maximum amount of heating or cooling energy from the exhaust air stream and return that energy to precondition the supply air. These systems, typically referred to as energy recovery ventilators, have generally been implemented in the colder regions of the United States, Canada, Europe, and Scandinavia.
In warm areas, there is not a significant energy dollar savings from using energy recovery ventilators since they are not as effective in the cooling season and they can be quite costly. That is, the cost of the additional electricity consumed by the system fans may exceed the energy savings from not having to condition the supply air in mild climates. Nevertheless, pollutants generated in a building, facilities, or institutions can accumulate and reduce the indoor air quality to unhealthful levels. In addition, regulations governing commercial facilities and institutions that require nearly one hundred percent outside air at high ventilation rates still apply in these warm areas.
Accordingly what is needed is a system and method for ensuring a healthy indoor environment and positive moisture control for an interior space in a variety of climates. What is further needed is a system and method for energy recovery that enable a facility's heating and cooling system to be downsized through lost energy recovery.